So, what is the difference between the EnerGuide FE rating and those other ratings?
The SS rating reported in manufacturers’ literature is the efficiency a fireplace can achieve were it placed in the middle of a room, radiating heat from all its surfaces, running continuously and suffering no energy losses. The AFUE rating averages out a unit’s efficiency over an entire heating season, selectively taking into account some energy losses but ignoring others. The EnerGuide FE rating reports a fireplace’s true energy efficiency by taking into account all its energy losses and by considering its overall performance during an entire heating season, not just on the day of testing.
